The present invention relates to a diaphragm for use in compressors and, more particularly, to a diaphragm formed with a sandwich structure to form an impermeable barrier to gases within a compressor.
Compressors for use in refrigeration systems often include a simple piston and cylinder configuration in which the piston draws refrigerant in through one port of the cylinder and pushes it out through a second port. The piston and cylinder must be provided with a lubricating oil and, in the absence of a barrier between the piston and the refrigerant fluid used in the system, oil will be found in the refrigerant thus decreasing the efficiency of the refrigeration system.
In an effort to separate the refrigerant from the oil lubricated parts, refrigeration compressors are provided with a diaphragm located above the piston and attached to the cylinder walls. The diaphragm is often in the form of a thin metal disk or a sheet of homogeneous flexible material positioned to flex away from and toward the input and output ports of the compressor to thereby force the refrigerant through the refrigeration system.
Diaphragms formed of metallic materials have been subject to early fatigue failure, particularly in the areas where the diaphragm is connected to the sides of the cylinder, and also require the piston to perform more work to overcome the stiffness of the diaphragm as the diaphragm is moved in and out to pump the refrigerant.
While diaphragms formed of homogeneous flexible materials have increased the efficiency of the pumping action due to their flexibility, and have reduced the problems associated with fatigue at the attachment points to the cylinder, these materials have proven to be relatively permeable and thus do not effectively separate the refrigerant from the lubricated parts of the compressor.
Accordingly, there is a need for a highly flexible diaphragm which is resistant to the permeability of gases such as Freon 502 which are used in refrigeration systems. Such a diaphragm must also be resistant to wear which may result from contact with the piston or with surfaces within the cylinder.
In addition, there is a need for an impermeable diaphragm which is capable of accommodating repetitive sharp flexures of the diaphragm material.